I can only guess the HD has SMART which in turn uses some on-bard logic. This in turn senses no track 0 or hell0f a error and won't allow further damage. This prevents a real trashing of data and it maybe too late to correct as you've removed bits&pieces. This is only a guess, unless you clipped some wiring too. The example you gave shown a HD drive but the actual mixer HD was a different one. I suspect it was much older like a 10 or 20gb HD. Maybe query them for further details may resolve your quest. But, I see the value if it all works. Of course you learn along the way.

tada ------Willy Happy